The impact of a particle on a transistor or close to a transistor may generate a stray current in an integrated circuit, depending on the ionizing power of this particle (for example characterized by its LET: Linear Energy Transfer). Indeed, the quantity of charge generated by a particle corresponds to that implemented during a change of state of a logic node controlled by a transistor. The consequence of this impact may be a change of state, or of levels, of the logic signals, and consequently give rise to errors at the output of the circuit.
In order to mitigate the errors generated by such phenomena, it is customary to duplicate the signals by duplicating the circuits which generate such signals. Such a redundancy makes it possible to reduce the probability of obtaining an erroneous signal at the output. Indeed, the probability of all the duplicated signals deriving from one and the same signal all being modified at one and the same time, that is to say of all the circuits generating these signals simultaneously undergoing a radiative disturbance, is much lower than the probability of an unduplicated signal being disturbed by external radiation. In this way, an analysis of the duplicated signals at the output makes it possible to retrieve the undisturbed value in a more reliable manner.
Certain business sectors, such as aerospace or the medical sector, need component robustness allowing close to 100% reliability of response, this characteristic outweighing the other factors.
It is known, in particular through the documents U.S. Pat. No. 6,703,858 or U.S. Pat. No. 5,570,313, to use electrical components named “C elements” to resolve these disturbances. As illustrated in FIG. 1, these C elements comprise, for example, a stack of four transistors, two PMOS transistors 11 and 12, and two NMOS transistors 13 and 14, coupled in series. The output signal of a logic block A0 is coupled at the input of the first PMOS transistor 11 and of the second NMOS transistor 14, and a second output signal of the logic block A1, corresponding to a duplication of the first signal A0, is coupled at the input of the second PMOS transistor 12 and of the first NMOS transistor 13. The output S is taken between the second PMOS transistor 12 and the first NMOS transistor 13.
These C elements are very good filters against errors induced by radiation. Indeed, if a disturbance occurs on just one of the two blocks, the two signals will be of contrary values, thus disabling any output signal. Indeed, if the signals deriving from the blocks A0 and A1 are different, no output signal will be emitted. However, these C elements have a weak output current and therefore a long response time for a given surface area. Other business sectors do not need such reliability, but on the other hand require more optimal criteria regarding speed of response, surface occupancy and power.